(1) Field of the Invention
The present invention relates to a device and a technical method for constructing a flight path in order to reach a destination.
The invention thus lies in the field of flight management and navigation systems for an aircraft, and more particularly for a helicopter, which field usually covers the functions of preparing a flight plan and of generating a flight path.
(2) Description of Related Art
It should be observed that the term “flight plan” is used to mean an ideal flight path that the aircraft ought to follow in order to reach its destination, passing via a plurality of waypoints. The flight path then comprises at least one segment joining together two successive waypoints.
Each segment is thus associated with a flying altitude and possibly also a speed of advance, a stage of flight, and a width for defining a flight corridor to be followed in order to go from one waypoint towards another waypoint.
It should be observed that document FR 2 875 901 proposes, in particular, overlaying at least one segment of a flight path on a map view, while also displaying a representation of geographical zones that might be dangerous for the aircraft.
Under such circumstances, it can be understood that the state of the art includes systems on board an aircraft or capable of being taken on board an aircraft that are suitable for constructing a safe flight path.
Nevertheless, such a system does not take the volume of noise emitted by an aircraft into consideration.
Nevertheless, this constraint is not negligible. More and more aircraft are flying close to built-up areas having high population densities and also to residential or tourist sites that are relatively less densely populated. Consequently, local authorities are tending to take legislative action to counter the noise nuisance caused by aircraft. Certain decisions thus seek to reduce air traffic around predetermined flights. A pilot who does not comply with the legislation may be called on to explain the reasons for infringing the regulations that are in place, and may possibly suffer sanctions.
It should be observed that the noise constraint is particularly applicable to rotorcraft since they fly at low altitude, whereas airplanes often fly at altitudes that are high enough to avoid significant and lasting noise nuisance on the ground being overflown.
Devices are thus known for use in real time in flight to assist a pilot in complying with legislation in terms of noise emission.
Thus, document FR 2 868 561 discloses a method and a device for minimizing the noise emitted during takeoff and landing of a rotorcraft.
Document WO 2008/112530 discloses a device acting on the power of an engine during takeoff in order to reduce the noise emitted by an airplane to the ground.
Document FR 2 906 912 proposes a method and a device for determining the level of sound nuisance outside an aircraft.
Document U.S. Pat. No. 7,383,104 suggests calculating the noise generated by an aircraft while taking environmental considerations into account.
Document US 2011/0001637 relates to a method of determining the noise level of a rotary wing aircraft. In that method, the torque of a power transmission device is used to determine the noise level.
Furthermore, documents US 2006/111818 and JP 9 254897 are also known.
Thus, the prior art describes firstly methods and devices for establishing a flight path and secondly methods and devices for informing a pilot in real time about the noise emitted by the aircraft or indeed for establishing reduced noise flight procedures, in particular on takeoff and landing.
Thereafter, in order to reach a destination, the pilot follows the various segments of the flight path and controls noise emission in order to attempt to comply with regulations in terms of noise nuisance.
It should also be recalled that piloting an airplane and more particularly a helicopter is an activity that is complicated.
A helicopter responds quickly and in lively manner to piloting orders given by the pilot using the flight controls, and the maneuverability of a helicopter is very high. Furthermore, piloting techniques vary depending on the stage of flight, these techniques being different for example between a stage of flight at low speed and a stage of cruising flight.
A helicopter thus requires a high level of attention from a pilot, since piloting requires accurate correcting actions to be taken without delay. The workload on an aircraft pilot, and more particularly on a helicopter pilot, is thus very large.
It can be understood that pilots and aircraft manufacturers are thus confronted with a technical problem that is particularly difficult to solve, namely that of reaching a destination while emitting only moderate noise over certain sites, i.e. noise below a threshold that generates a small or zero sound footprint on the ground. It is difficult for a pilot to divert attention from piloting proper in order to take into consideration information relating to the noise emitted by the aircraft.
Furthermore, it should be observed that during a flight, a pilot's freedom of action is sometimes limited, e.g. by the amount of fuel available. As a function of this amount and of the fuel consumption of the power plant, a pilot is sometimes not able, without endangering the mission of the flight, to fly around a site that is the subject of strict legislation concerning noise nuisance.
From an extreme point of view, real time management of noise by a pilot otherwise occupied with vital aircraft-control tasks can actually be dangerous, since the pilot may need to depart from a flight path in order to limit noise emission over a site, with that being done to the detriment of safety.